EP0133911A2 - Process for the preparation of trans-1,1,2,3,4,4-hexabromo-2-butene by bromination of diacetylene - Google Patents

Abstract

1. A process for the production of trans 1,1,2,3,4,4-hexabromo-2-butene by bromination of diacetylene, characterised in that the diacetylene from the hydrocarbon residue arising in the acetylene recovery operation is dissolved at a temperature of -20 degrees C to + 20 degrees C and a pressure of 1 to 2 bar in a solvent containing a hydroxyl group, initially a mixture rich in vinylacetylene is separated off in a first desorption stage at a temperature of 0 to 30 degrees C and a pressure of 1 to 2 bar with an inert gas, then a gas mixture rich in diacetylene is desorbed in a second desorption stage at a temperature of 0 to 30 degrees C and a pressure of 1 to 2 bar with an inert gas, this diacetylene-rich gas mixture is brominated in a reactor in which excess bromine dissolved in a halohydrocarbon has previously been placed, water optionally being added to the halohydrocarbon, at a temperature of 20 to 40 degrees C and a pressure of 1.2 to 2 bar to form trans 1,1,2,3,4,4- hexabromo-2-butene, gaseous bromine being additionally fed to the reactor with the reaction gas, and the bromine-containing offgas is optionally reacted in an after-reactor with excess diacetylene in a halohydrocarbon.

Description

The invention relates to a process for the safe production of trans-1.1.2.3.4.4-hexabrom-2-butene (HBB) by bromination of diacetylene.

HBB has excellent flame-retardant properties and is therefore a sought-after compound for the manufacture of flame-retardant plastics. So far, however, no technically applied process is known for producing this compound in a safe manner by bromination of diacetylene.

Due to its tendency to explode, diacetylene is used almost exclusively for the manufacture of laboratory preparations in correspondingly small quantities. For example, the literature recommends using a maximum of 10 g of diacetylene in reactions with diacetylene for safety reasons ( _S hostakovskii and Bogdanova "The Chemistry of Diacetylenes" 1974, Keter Publishing House Jerusalem Ltd.).
DE-AS 21 57 538 (= GB-PS 1 360 050) "Process for the production of polychlorinated or polybrominated aliphatic hydrocarbons" describes the halogenation of mixtures of gaseous acetylene compounds. However, this method is impracticable in wide ranges that are within the explosion limits. According to the information in this document, in addition to many other halogenated hydrocarbons, a hexabromobutene isomer is obtained, although only 1.1.2.2.3.4-hexabromobutene-2 with a melting point of 198 ° C.

A major disadvantage of this process is the high volume of liquid halogenation products, which are extremely toxicologically unsafe. A corresponding loss of halogen is also associated with the accumulation of these worthless compounds. The method in which the mixture of the acetylenes to be halogenated is obtained is also extremely disadvantageous and questionable in this process. A gas stream containing diacetylene, vinyl acetylene, methyl acetylene, acetylene and butadiene is passed over activated carbon until the carbon is saturated. Here, a mixture is adsorbed on the activated carbon, which is composed as follows according to the information in Example 1:

Such high concentrations of the higher acetylenes cannot be safely handled technically. The enthalpy of adsorption released during adsorption on activated carbon also promotes the polymerization of these acetylenes. Polymers of diacetylene explode in the heat or after prolonged storage (Shostakovskii and Bogdanova "The Chemistry of Diacetylenes" 1974, Keter Publishing House Jerusalem Ltd.).

This gave rise to the task of developing a process which can be carried out safely for the production of trans-1.1.2.3.4.4-hexabrom-2-butene by bromination of diacetylene with the least possible formation of other bromocarbons and the least possible loss of bromine.

This object is achieved according to the information in the claims, surprisingly obtaining the desired trans-1.1.2.3.4.4-hexabrom-2-butene in high yield and purity. In the absorption column, the residual hydrocarbons containing the diacetylene and other acetylenes such as vinyl acetylene and methyl acetylene are at temperatures from -20 ° C to +20 ° C, preferably -15 ° C to 0 ° C, in particular -10 ° C to -5 ° C, and pressures from 1 bar to 2 bar, preferably at 1 to 1.5 bar, with a hydroxyl-containing solvent, for example methanol. The running solution essentially contains diacetylene, vinyl acetylene and methyl acetylene in dissolved gases. In general, 0.0005 to 0.003 parts by volume of the hydroxyl-containing solvent / part by volume of the residual hydrocarbons are used, preferably 0.001 to 0.002 parts by volume of the solvent / part by volume of the residual hydrocarbons. Suitable solvents containing hydroxyl groups are, for example, methanol and / or ethanol.

This solution is mixed with an inert gas, such as. B. nitrogen or methane in a first desorption stage at temperatures from 0 ° C to 30 ° C, preferably 10 to 25 ° C, in particular at 20 ° C, and pressures of 1 to 2 bar, preferably 1.1 to 1.5 bar , in particular 1.2 bar, with the gas phase containing a relatively high concentration of the dissolved acetylenes, in particular vinyl acetylene, relative to the diacetylene. In general, 30 to 100 parts by volume of inert gas / part by volume of solution are used, preferably 50 to 70 parts by volume of inert gas / part by volume of solution. Examples of suitable inert gases are nitrogen, hydrogen, the noble gases such as helium, neon, argon and gaseous alkanes such as methane, ethane, propane and mixtures thereof.

The methanol solution running off contains a relatively large amount of diacetylene in addition to only a little vinyl acetylene and practically no more methyl acetylene. This solution is a more suitable starting mixture for the bromination of the diacetylene contained therein.

However, the direct bromination of this solution only leads to liquid bromination products, such as. B. tetrabromobutadiene, while the amount of hexabromobutene is very low. Surprisingly, however, it was found that very good yields of hexabromobutene are obtained if the diacetylene is removed from the methanolic solution in a second desorption stage at temperatures from 0 to 40 ° C., preferably at 10 to 30 ° C., in particular at 20 to 25 ° C. , and pressures of 1 to 2 bar, preferably at 1.2 to 1.6 bar, in particular at 1.4 bar, with an inert gas, such as. As nitrogen or methane, desorbed.
In general, 90 to 250 parts by volume of inert gas / part by volume of solution are used, preferably 120 to 170 parts by volume of inert gas / part by volume of solution. Suitable inert gases are, for example, nitrogen, hydrogen, the noble gases such as helium, neon, argon and gaseous alkanes such as methane, ethane, propane and mixtures thereof.

The gas stream obtained in the desorption is fed to the bromination. The gas stream contains diacetylene in a concentration that no longer poses a danger from an otherwise possible self-decomposition (below 10%) and significantly less _v inylacetylene (approx. 10% of the amount of diacetylene).

The bromination is carried out in a halogenated hydrocarbon at temperatures of 20 to 40 ° C., preferably 25 to 35 ° C., in particular at 30 ° C., and pressures of 1.2 to 2 bar, preferably 1.3 to 1.6 bar, in particular at 1.4 bar, through.

Suitable halogenated hydrocarbons are, for example, carbon tetrachloride, carbon tetrachloride and / or chloroform, preferably carbon tetrachloride.

The bromination can take place in generally customary reactor types, for example in a stirred reactor. In a preferred embodiment of the process of the invention, bromination is carried out in a bubble column reactor in which a halogenated hydrocarbon, such as, for. B. tetrachloroethane, preferably carbon tetrachloride, with bromine dissolved in the halogenated hydrocarbon. The concentration of dissolved bromine is generally 0.1 to 2% by weight, preferably 0.3 to 0.5% by weight.

However, if the reaction is carried out in this way, after a relatively short time a decrease in the formation of hexabromobutene and an increase in the formation of liquid bromination products are observed. Surprisingly, it has now been found that the yield of trans-1.1.2.3.4.4-hexabrom-2-butene remains unchanged when water is added to the halogenated hydrocarbon in an amount of 10 to 100% of its volume, preferably 20 to 40% by volume. , in particular 25 to 35 vol .-%, is added.

Corresponding to the consumption of bromine, which can be observed from the change in color, the bromine is simultaneously fed in in such an amount that the excess set at the beginning is maintained. This excess is generally 0.1 to 2 wt .-%, based on the halogenated hydrocarbon.

This means that the exhaust gas discharges small amounts of bromine from the reactor. In order to avoid this loss of bromine, the exhaust gas can be passed through a post-reactor in which, as in the main reactor, there is a chlorinated hydrocarbon as solvent. A small partial flow of the reaction gas is introduced into this post-reactor simultaneously with the exhaust gas from the reaction. With the diacetylene now present in excess, the bromine present in the exhaust gas is in turn converted to trans-1.1.2.3.4.4-hexabrom-2-butene, so that the exhaust gas from the after-reactor no longer contains any measurable amounts of bromine.

If the reaction is carried out in a bubble column reactor, the lower part of the reactor, designed as a collecting vessel, fills with the crystalline trans-1.1.2.3.4.4-hexabromobutene formed and is finally discharged from the latter for the purpose of working up.

For working up, the hexabromobutene is suctioned off in a suitable transfer device, for example in a glass suction filter, then washed with an alcohol, for example methanol or ethanol, and finally dried in vacuo.

The trans-1.1.2.3.4.4-hexabrom-2-butene with a melting point of 181 ° C., which corresponds to that given in the literature (Müller, Helv. 8, 831), is obtained in high purity with a good yield. The HBB obtained is particularly suitable as a flame-retardant additive to plastics.

example 1

und folgende Zusammensetzung hat:

9,1 m³/h dieses Gases werden in dem Absorber 8 bei einer Temperatur von -5 °C und einem Druck von 1,2 bar mit 13 1/h Methanol gewaschen.
Man erhält eine methanolische Diacetylenlösung ② mit der folgenden Zusammensetzung:

A residual gas is used, which is obtained in the production of acetylene by the arc process

and has the following composition:

9.1 m ³ / h of this gas are washed in the absorber 8 at a temperature of -5 ° C and a pressure of 1.2 bar with 13 1 / h of methanol.
A methanolic diacetylene solution ② with the following composition is obtained:

This methanolic solution is moved to the desorption column 9 and desorbed at 25 ° C. and 1.2 bar with 800 Nl / h nitrogen. The running methanol solution lauf has the following composition:

In a second desorber 10, the solution ③ is desorbed with 2500 Nl / h nitrogen at 20 ° C. and 1.5 bar. The running solution 4 is returned to the absorber 8, the reaction gas ⑤ is passed into the reactor 11 in which 80 l of carbon tetrachloride with a bromine content of 0.3% by weight and 20 l of water are initially introduced.

Brom wird sofort aufgenommen, entsprechend dem Verbrauch wird so viel Brom in den Reaktor gepumpt, daß der Überschuß von 0,3 % gehalten wird (ca. 2,9 kg/h). Durch die Mantelkühlung des Reaktors wird die Temperatur bei etwa 30 °C gehalten. Der Druck im Reaktor beträgt 1,5 bar. Nach einer halben Stunde beginnt das trans-1.1.2.3.4.4-Hexabrom-2-buten aus der Lösung auszufallen und sammelt sich im unteren Teil des Reaktors. Nach 8 Stunden Fahrzeit wird es abgelassen und aufgearbeitet. Dazu wird es in einer Glasfilternutsche abgesaugt und anschließend mit insgesamt 5 1 Methanol gewaschen. Anschließend wird es im Wasserstrahlvakuum in derselben Apparatur getrocknet.The reaction gas 5 has the following composition:

Bromine is taken up immediately; according to consumption, so much bromine is pumped into the reactor that the excess of 0.3% is maintained (approx. 2.9 kg / h). The jacket cooling of the reactor keeps the temperature at about 30 ° C. The pressure in the reactor is 1.5 bar. After half an hour, the trans-1.1.2.3.4.4-hexabrom-2-butene begins to precipitate out of the solution and collects in the lower part of the reactor. After 8 hours of driving, it is drained and worked up. For this purpose, it is suctioned off in a glass suction filter and then washed with a total of 5 liters of methanol. Then it is dried in a water jet vacuum in the same apparatus.

From 23.5 kg of bromine, 20 kg of trans-1.1.2.3.4.4-hexabrom-2-butene are obtained, which corresponds to a yield of 77% (based on bromine).

Example 2

10 m ³ / h of a residual gas with the composition given in Example 1 are washed in the absorber 8 at a temperature of -10 ° C and a pressure of 1.5 bar with 20 1 / h of methanol.

A methanolic diacetylene solution 2 with the following composition is obtained:

This methanolic solution is driven onto the desorption column 9 and desorbed at 25 ° C. and 1.4 bar with 1 200 Nl / h methane. The running methanol solution 3 has the following composition:

Solution 3 is now desorbed into the desorber 10 at 25 ° C. and a pressure of 1.3 bar with 3 500 Nl / h of methane.

The running solution 4 is returned to the absorber 8, while 3,200 Nl / h of the reaction gas 5 are passed into the reactor 11. This contains 60 1 chloroform with a bromine content of 0.5% by weight and 30 1 water.

Der Druck im Reaktor beträgt 1,3 bar, die Temperatur wird bei ca. 25 °C gehalten. Die Reaktion setzt praktisch sofort ein, durch Ergänzen von ca. 3,6 kg Brom/h wird der Überschuß von etwa 0,5 Gew.-% Brom gehalten. Das Abgas 6 wird in den Nachreaktor 12 geleitet, in dem 40 1 Chloroform vorgelegt sind und in den gleichzeitig 300 N1 des Reaktionsgases 5 eingeleitet werden. Das im Abgas 6 enthaltene Brom setzt sich im Nachreaktor 12 mit dem im Reaktionsgas 5 enthaltenen Diacetylen wie im Hauptreaktor 11 zu Hexabrombuten um. Das Abgas 7 aus dem Nachreaktor ist praktisch bromfrei.The reaction gas 5 has the following composition:

The pressure in the reactor is 1.3 bar, the temperature is kept at approx. 25 ° C. The reaction starts almost immediately, by adding approx. 3.6 kg bromine / h Excess of about 0.5 wt .-% bromine kept. The exhaust gas 6 is passed into the after-reactor 12, in which 40 liters of chloroform are placed and into which 300 Nl of the reaction gas 5 are simultaneously introduced. The bromine contained in the exhaust gas 6 is converted in the post-reactor 12 with the diacetylene contained in the reaction gas 5 as in the main reactor 11 to hexabromobutene. The exhaust gas 7 from the post-reactor is practically free of bromine.

After 8 hours of driving, the hexabromobutene formed is discharged both from the main reactor 11 and from the post-reactor 12 and worked up together. After washing with about 5 l of methanol, the hexabromobutene is dried in vacuo.

From the 29.5 kg of bromine used, 26.5 kg of trans-1.1.2.3.4.4-hexabrom-2-butene with a melting point of 182 ° C. are obtained, which corresponds to a yield of 81% (based on bromine).

Claims (6)

1. Process for the preparation of trans-1.1.2.3.4.4-hexabrom-2-butene by bromination of diacetylene,
characterized,
that from the residual hydrocarbons obtained in the production of acetylene, the diacetylene is dissolved in a hydroxyl-containing solvent at temperatures from -20 ° C to + 20 ° C and pressures from 1 to 2 bar, in a first desorption stage with an inert gas at temperatures of 0 to 30 ° C and pressures of 1 to 2 bar first separate a mixture rich in vinyl acetylene, then in a second desorption step with an inert gas at temperatures from 0 to 30 ° C and pressures of 1 to 2 bar desorb a gas mixture rich in diacetylene, this in one Reactor in which excess bromine is initially dissolved in a halogenated hydrocarbon, water being optionally added to the halogenated hydrocarbon at temperatures of 20 to 40 ° C. and pressures of 1.2 to 2 bar to give trans-1.1.2.3.4.4-hexabrom-2 -Butene brominated, with additional gaseous bromine being added to the reactor with the reaction gas, and the bromine-containing exhaust gas optionally in a post-reactor with excess m converts diacetylene into a halogenated hydrocarbon. 2. The method according to claim 1, characterized in that
that methanol and / or ethanol is used as the solvent containing hydroxyl groups. 3. The method according to claim 1 and 2,
characterized,
that carbon tetrachloride and / or chloroform is used as the halogenated hydrocarbon. 4. The method according to claims 1 to 3,
characterized,
that water is added to the halogenated hydrocarbon in an amount of 10 to 100% by volume, preferably 20 to 40% by volume. 5. The method according to claims 1 to 4,
characterized,
that the brominated diacetylene at temperatures of 25 to 35 ° C. 6. The method according to claims 1 to 5,
characterized,
that one carries out the bromination in a bubble column reactor.

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